The present invention relates to climate control, i.e., air conditioning cooling and heating of the cabin of an aircraft.
The temperature of the air in an aircraft cabin is usually controlled by means of pressurized air taken (i.e., tapped) from a compressor stage in one of the engines, unless a separate compressor is provided for that purpose. One should tap the engine compressor only if, thereby, the power of the engine is not, or only very insignificantly, reduced. Military aircraft have a comparatively small cabin so that the air requirements for climate control can, indeed, be satisfied from an engine compressor without loss in power. However, military aircraft are to an increasing extent "loaded" with sensitive electronic equipment which must also be climatized. Safety of the aircraft as well as completion of the assigned mission depends on the proper working of this equipment. Thus, inspite of a small crew cabin, one does also need a large amount of air for climate control of a military aircraft, and interference with the power requirement of propulsion may be expected if an engine were to be tapped.
The situation is different for commercial, i.e., passenger, aircraft, but with a similar result. A modern passenger plane has a large passenger cabin and requires considerable quantities of air on that account alone. It can thus be seen that the practice of tapping the engine compressor for climatizing the plane appears to be no longer an attractive approach.